Square filters (COKIN)

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ivankathy14

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Ivan
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Recently I found a photo that caught my attention. A very stunning photograph of sunsets with some silhouettes of peoples and the sky with very high dynamic range; very intense colors in them, sometimes blue, purple, orange to yellow and so on.

At first I thought it was photoshoped because for me,who knows a little about photography who just shoots and edit it in photoshop, it was impossible but when I asked him how did it. He just said that "G-ND8" filters. I was curious about it and did a little research and learned that Gradient Neutral Density filters are the culprit for this very stunning images but still, I haven't learn all the tecnical details about it. How and when to use it, what GND filter should I use 8, 4, 2, 8 soft? I still don't fully understand this kind of filter; does other colors filter like orange, purple or blue adds/boost colors in the horizon at sunsets, dawn or even daytime?
 
Graduated filters help to bring the dynamic range of a scene within what a digital(or film) camera's sensor can capture. Dynamic range of a camera is roughly (i think) 7 or 8 'stops'.
If a foreground in a picture requires, say an exposure of 1/125 at f16 ISO 100 but the sky, being much brighter would require a setting of 1/500 at f16 100 ISO then you have 2 "stops" of difference and the total range of "stops" across the picture(from the darkest shadow to the brightest highlight) might be in excess of 9 or 10. So in this case you could select a 2 stop graduated filter, (0.6, ND4) This "holds back" the sky's exposure to roughly the same as that needed for the foreground. Why 2? Because there are 2 stops between 1/125 and 1/500 shutter speed.
The "ND" in ND8 stands for neutral density, ie they shouldn't introduce any colour cast as their colour is neutral. So your man did not use the filter to get the colours you saw. In this case the 8 in ND8 means the filter has 3 stops reduction. i.e. in the example above the sky would have required 1/1000 f16 ISO 100.
(1 stop reduction or "hold back" = 0.3 or ND2, 2 stop = 0.9 or ND4, 3 stop = 0.9 or ND8)

Does that help? Im not the best at explaining things I admit! :thinking: Try looking here as well
http://en.wikipedia.org/wiki/Graduated_neutral_density_filter

Perhaps someone a bit more eloquent will be along to do a better job than me shortly! :D

HTH
 
As above, but you can also get coloured grads to get different tones. Lee do several kits for different things, like the Landscape kit which has different coloured grads, straw kit, coral kit, blue kit etc. They also make "stripe" filters which is just a thin band of colour through the centre of the filter for sunsets shots.

Often you will find a Standard ND grad will bring out colour in the sky thats already there, but lost in the brightness. The coloured filter can be used to enhance the natural colour, or add colour where there isnt any at all.

Grads come in hard and soft. Lee reccomend to use Hards for most things, but other will say otherwise. You should ideally have both for different situations. Softs are usefull for landscapes where there is noe definate horizon line. Hards are more suited for seacapes etc.
The strength depends on the light at the time. If the sky is 2 stops brighter, use a 2 stop.. If its 4 stops brighter use a 3 stop and a 1 stop together.
Most people could get by with 1 Hard 0.6 grad, as that usualy does enough to control the sky enough to be able to recover it in PP afterwards, but ideally you want to get it right in the camera, so having full kits of both soft and hards will cover you for every situation.
 
Grad filters are useful if you do a lot of landscapes. I bought one when I went on holiday, but I don't do a lot of landscapes. Useful, not essential in the world of digital. I prefer to try and get it right in shot, if possible. Quite cheap, really.
 
Thanks for the tip everyone. I think i understand the concept a little bit! Again thanks!

Cheers! :)
 
Thats actually very well explained. Toying with getting some ND grads myself.
 
Bought an adapter ring(67mm) in my case and a cokin p style filter holder. Not cokin branded but as far as I can tell it's good quality in terms of fitting snug etc. Very cheap from fleabay.
 
Sorry I don't know how to edit on the app version of the forum yet...... Should add that cokin p filter holder takes 85mm filters so that's why i went for 85mm hitech filters.
 
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